Crossover from Metallic to Semiconducting in Pb_2-xLn_xRu₂O_7-δ (Ln = Eu, Sm) Compounds with Pyrochlore Structure

Abstract:

We study the synthesis and physical properties of Pb2-xLnxRu2O7- (Ln = Sm, Eu) compounds with pyrochlore structure. The lead-lanthanoid pyrochlores Pb2-xLnxRu2O7- (Ln = Sm, Eu) have been successfully synthesized by the solid-state reaction. All samples were characterized by X-ray diffraction, magnetic susceptibility, and electrical resistivity measurements. Magnetic susceptibility measurements showed that the spin-glass transition temperature, TSG, decreases with Ln content x and goes to zero at x = 0.2 and 0.6 for Sm and Eu, respectively. From electric resistivity measurements, a crossover from metallic to semiconducting behavior was observed in the range of 0.2 ≤ x ≤ 0.4 and 0.4 ≤ x ≤ 0.8 in Pb2-xSmxRu2O7- and Pb2-xEuxRu2O7-, respectively. These boundaries between metallic and insulating phases mostly correspond to values of x with TSG = 0. These metal-insulator transitions can be caused by the strongly correlated couplings between the itinerant 4d electrons which are possibly attributed to the magnetic frustration.

• Periodical: Materials Science Forum (Volumes 631-632)
• Pages: 483-488
• DOI: https://doi.org/10.4028/www.scientific.net/MSF.631-632.483
• Online since: October 2009
• Authors: Kato Masaki, Tetsuya Imamaura, Miho Fukatsu, Hirota Ken
• Keywords: Electric Resistivity, Magnetic Susceptibility, Metal-Insulator Transition, Pyrochlore Structure, Ruthenate, Strongly Correlated Electron System

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